A method for the construction of carb'on paste electrodes (CPE) is described. Here ferrocene is used as the insoluble electroactive species, graphite powder as conductor and sulfuric acid as binder. The CPE thus prepared prevents ferrocenium ions from diffusing towards the bulk solutions. Voltammetric, chronolpotentiometric and chronoamperometric experiments performed with these CPEs show that the different preparation methods yield different electrochemical parameters for the ferrocene-ferrocenium system.

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Seven cationic surfactants: 1-methyl-3-tetradecyl imidazolium bromide, 1-methyl-3-hexadecyl imidazolium bromide, N,N-tetradecyl pyridinium bromide, N,N-hexadecyl pyridinium bromide, N,N-dimethyl-N-ethylbenzyl ammonium bromide, N,N-dimethyl-N-ethylbenzyl ammonium laurate and N,N-dimethyl-N-ethylbenzyl ammonium acetate, were investigated at different doses (10, 25, 50, 100, and 200 ppm) as corrosion inhibitors for steel grade API 5L X52 in hydrochloric acid 2 M using a weight loss technique, impedance and polarization resistance methods. The corrosion inhibition of steel grade API 5L X52 of the cationic surfactants was attributed to their molecular structure (heterocyclic ring, hydrophobic chain length and counterion) that enhances adsorption onto steel surface. The best protective efficiency of the film was higher than 90% (N,N-Dimethyl-N-ethylbenzyl ammonium acetate). It is important to know how organic inhibitor films grown on the metallic surface in order to achieve superior corrosion inhibition, hence experimental findings were described by Langmuir adsorption isotherm. The Electrochemical Impedance Spectroscopy spectrums were fitted by means of the Voigt model.

A kinetic study for the electrosynthesis of polypyrrole (Ppy) doped with SO 4 -2 ions is presented. Ppy films are electrochemically polymerized over graphite -epoxy resin electrode. Cyclic voltammetry shows a non-reversible process and the charge density increases as the number of cycles increases too. Current transients are obtained for three different potentiometric behaviors: anionic, cationic and a combination of both. Experimental data was statistically fitted to theoretical models to determine the nucleation and growth processes governing the polymer synthesis. Statistical fit suggests that the mechanism involved in the electropolimerization process is 3D nucleation limited by diffusion of the electroactive specie. The anionic-response polymer displays the lowest diffusion coefficient, while the cationic-response polymer displays the highest one. In all cases, both the active-sites number and the nucleation rate have considerably high values.

In this work, we shown the electrochemical detection of serotonin (SR) in the presence of dopamine (DA), using a carbon paste electrode (CPE) modified with gold nanoparticles (NPs). The gold NPs were synthesized by the chemical method with b - cyclodextrin (AuNPs-b CD). Electrochemical treatment was applied to the electrode surface to distinguish between the oxidation signals of SR and DA. Electrochemical changes of the CPE surface were performed by forming multiple layers of AuNPs-b CD by cyclic voltammetry. The separation of oxidation peaks associated with the signals of SR and DA in acidic medium is shown in Figure 1. The results demonstrate that the film formation on the electrode inhibits the electrode surface passivation via the adsorbed species, which arise during the SR oxidation process. The electroanalytical determination was carried out using the electrochemical techniques: cyclic voltammetry (CV), differential pulse voltammetry (VDP) and square wave voltammetry (SWC).